The present invention relates generally to complex fabrics comprising a chopped glass-fiber strand mat. The complex fabrics further include one or more layers of continuous glass-fiber rovings and a tissue-paper backing layer supporting the chopped-strand mat. The various layers are stitch-bonded together to form the complex fabric.
The fabrics may be used in a variety of applications, e.g., as reinforcing components in plastic molded parts or composite products. For example, the inventive fabrics may be wetted out or impregnated with suitable resins to manufacture poles (e.g., light or telecommunication poles), baths and lavatories, automobile and van roofs, profiles, bumpers, engine covers, blades (e.g., for windmills), and skis and snowboards.
Complex fabrics comprising layers of glass-fiber rovings are generally known in the industry. For example, the use of glass fibers in paper-making has long been known (see. e.g., U.S. Pat. No. 5,318,844 to Brandon). High-temperature resistant fibers have been made into flexible fabrics or papers which provide dimensional stability, fire resistance, and flexural strength. These papers have been made using conventional paper-making production equipment where staple fibers are laid in uniform layers, consolidating the fiber layers into a paper or fabric.
These multi-layer, complex fabrics are usually supported by a chopped-strand mat comprising a layer of randomly-laid strands of glass fibers. Many known processes for making the chopped-strand mat require using a binder, adhesive, glue, or other moisture-containing paste to join the fibers and form the chopped-strand mat. These processes require a step of drying or curing the binder, adhesive, glue, or paste. Thus, such processes involve the use of additional material and require additional time in producing a complex fabric.
A variety of complex or composite fabrics are known. U.S. Pat. No. 4,499,134 to Whitely et al. discloses a composite comprising a paper, which has a thickness of about 0.01 inch to 0.05 inch (about 0.254 mm to 1.27 mm) and a bulk density of between 5 and 15 lb./ft3 (80.092 and 240.277 kg/m3), and an abrasion-resistant, high-temperature scrim, which may be composed of fibers such as glass fibers, disposed on one or more surfaces of the paper. U.S. Pat. No. 4,983,453 to Beall discloses a composite pultruded product made from glass roving strands and a cellulosic mat having a basis weight generally falling between about 100 g/m2 and 800 g/m2.
Although various complex fabric materials are known, there is a need for complex fabrics having enhanced wetting out or impregnation by resin when used to manufacture reinforced composite products. Additionally, there is a need for relatively low-cost fabrics having advantageous wet-out and impregnation properties.
Furthermore, there exists a need for an improved complex fabric that eliminates the need for binders, adhesives, or pastes in forming a chopped-strand mat which supports the multiple layers of the complex fabric. There is also a need for a process for making such multi-layer complex fabrics which eliminates a drying or curing step during the making of the chopped-strand mat for the complex fabric.
An object of the invention is therefore to achieve a complex fabric having improved wet-out that may be made at a low cost. Another object is to provide a method of making a multi-layer complex fabric wherein the mat is made without the need for drying or curing.
Such objects are achieved by the complex fabric of the present invention, which comprises a chopped glass fiber or strand mat, a tissue-paper backing layer, and at least one layer of glass-fiber rovings, which are preferably made from continuous fibers. The chopped glass fiber strand mat has two lateral surfaces and comprises randomly laid and oriented glass-fiber strands. The tissue-paper backing layer is disposed on a first lateral surface of the chopped-strand mat, supporting the mat. The chopped-strand mat preferably contains essentially no adhesive, binder, paste, or glue. Each roving layer preferably includes a plurality of glass-fiber rovings arranged in a unidirectional fashion along an axis of the complex fabric. The glass-roving layers overlay an opposed lateral surface of the chopped-strand mat. The various layers of the complex fabric, i.e., the tissue-paper backing, chopped-strand mat, and glass roving layer(s), are stitch-bonded together to form the complex fabric.
A preferred embodiment of a method for making a multi-layer complex fabric of the present invention comprises providing a tissue-paper backing layer and laying chopped glass-fiber strands over the tissue-paper layer in a randomly laid and oriented fashion, thereby forming a chopped-strand mat over a lateral surface of the tissue-paper backing layer. Next, continuous glass-fiber rovings are laid onto the chopped-strand mat, forming a roving layer, and then the tissue-paper backing layer, chopped-strand mat, and glass-fiber roving layers are stitched together to form the complex fabric.
An advantageous feature of the inventive fabric is improved wet-out and impregnation by polymer resin when used as a reinforcement in the manufacture of composite products. The resin more readily wets out and impregnates the complex fabric because the tissue-paper layer enhances the absorbency of the fabric as a whole. Moreover, holes formed in the fabric by the stitching, as well as openings between the chopped glass fibers in the mat, help enhance resin impregnation. Additionally, a cost reduction is achieved through the use of a low-cost backing material. In comparison, known materials used as backings for glass-fiber mat or complex fabrics are not only more costly, but provide no improvement in wet-out performance.
These and other advantages, objects, and features of the present invention will be apparent from the following detailed description in conjunction with the attached drawings.